\(\lim\limits_{x\rightarrow-\infty}\dfrac{x^2+2x+4}{\left|2x+1\right|}\) bằng
\(12\).\(10\).\(+\infty\).\(-\infty\).Hướng dẫn giải:Khi \(x\rightarrow-\infty\) thì \(2x+1< 0,\left|2x+1\right|=-2x-1,\frac{x^2+2x+4}{\left|2x+1\right|}=\frac{x^2+2x+4}{-2x-1}=\frac{x+2+\frac{4}{x}}{-2-\frac{1}{x}}\) do đó
\(\lim\limits_{x\rightarrow-\infty}\frac{x^2+2x+4}{\left|2x+1\right|}=\lim\limits_{x\rightarrow-\infty}\frac{x+2+\frac{4}{x}}{-2-\frac{1}{x}}=+\infty\)